The present invention concerns solar powered road markers.
The following information is provided solely to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art to the present invention.
In most applications, the current road markers are small, rectangular housings that include a reflective material arranged such that light from the headlights from an approaching motor vehicle will be reflected back to the driver, thereby enhancing visibility of the marker. In many cases, the housing is mounted on the road surface or in a small depression in the road surface, typically using an adhesive. However, such reflective road markers do not function well under some adverse conditions, such as inclement weather, e.g., foggy conditions, or where an appreciable coating is present on the surface of the marker, as such conditions substantially reduce the amount of light that is effectively reflected from the marker back to the vehicle driver.
One way of addressing such difficulties is to use a marker with an internal light source rather than relying solely on reflected light. While markers utilizing wires to supply power for the light source can be constructed, such markers are expensive to install and maintain. An alternative is to use a self-contained marker that has an internal power supply. Such internal power supply can be designed to utilize one or more photovoltaic devices (also referred to as solar cells) and an energy storage device such as a rechargeable battery.
A number of different solar powered road markers have been described. For example, Lee, U.S. Pat. No. 4,050,834 describes an internally powered traffic control device that includes a support member, a solid state light emitting device such as a light emitting diode (LED), a power supply such as a rechargeable battery pack, a solar cell, and a network for controlling the energization of the LED.
Roberts, U.S. Pat. No. 4,668,120 describes a solar powered illuminated reflector that includes a housing, at least one reflector element, a light source, a window member or lens for transmitting light outward from the light source in a predetermined direction, and a photovoltaic power system.
Parashar, U.S. Pat. No. 5,984,570 describes a self energized automatic surface marker that includes a housing, one or more LEDs, and a solar powered energy storage system that includes solar cells and 5–10 storage capacitors.
Green et al., U.S. Pat. No. 5,782,552 describes a light assembly that includes a LED, a capacitor to energize the LED, and a solar cell to charge the capacitor. The patent indicates that in a particularly desirable aspect, the light assembly is housed in a plexiglass shell and potted with appropriate potting compounds.
Chen, U.S. Pat. No. 5,703,719 describes a reflector road sign with self-provided light means. The reflector road sign includes a reflector body made of tempered glass, a casing made to receive the reflector body, a solar lighting system that includes a LED, a rechargeable battery, a control circuit, and a reflecting device mounted around the LED lamp.
WO 01/42567 (PCT application PCT/KR00/01425) describes a road stud using a solar cell. The road stud has a portion that is embedded in the road, and an upper light emitting portion.
WO 01/58219 (PCT application PCT/IL01/00083) describes a method for reducing energy consumption of LED illuminated road markers, and road markers that utilize that method. The energy consumption is said to be reduced by supplying current pulses to an LED, where each pulse is characterized by having a pick value higher from the nominal working current value of the LED, and the duty-cycle of the of the pulses is correspondingly short, such that the LED is provided with an effective current within its permitted current range.
Rogers, U.S. Pat. No. 4,314,198 describes a solar power source for a light system.
Each of the references cited above is incorporated herein by reference in its entirety, including drawings.